Sonic signaling device



W. K. FORTMAN ETAL SONIC SIGNALING DEVICE March 24, 1964 2 Sheets-Sheet1 Filed Nov. 15, 1962 INVENTORS. WILLIAM K. FORTMAN NORMAN C PICKERINGMarch 24, 1 w. K. FORTMAN ETAL SONIC SIGNALING DEVICE 2 Sheets-Sheet 2Filed NOV. 15, 1962 INVENTORS. WILLIAM R FoRmAfi' BY NORMAN c. PICKERINGFIG. 3

ATTOR NEY United States Patent 3,125,986 SONIC SIGNALING DEVECE WidiiarnK. Fortman, 186 Cold Spring Road, Syosset, N.Y., and Norman C.Pickering, Sag Harbor, N .Y. Filed Nov. 15, 1962, Ser. No. 237,927 13Claims. (Ci. 116-437) This invention relates to pulsed sound sources andin particular to means for producing a modulated sonic energy beam bymeans of a jet stream excited acoustical generator.

As disclosed in Yellott and Savory Patent No. 2,519,- 619, a gaseous jetstream may be directed from a nozzle into an opposed acousticallyresonant cavity to generate sonic energy. The high intensity sonic waveenergy field so generated finds many useful applications in spraydevices, foam breakers, tank cleaning and the like, wherein a steadystate sonic wave is maintained. The present invention, however, isdirected towards an intermittent, selectable operation of such cavityresonators whereby the operation may be almost instantaneously haltedand then regenerated, thus converting the resonator into a signal orcontrol device responsive to programming. The utility of such a devicewill be apparent to those skilled in the art since sonic generators, ingeneral, are very diflicult to regulate in terms of starting andstopping. Whistles, sirens, and the like, require a considerable timeinterval for regeneration of the sound once the device is stopped, andmoreover, this interval is unpredictable. The use of standard cavityresonators, such as the Hartmann type, presents difiicultieis inpractice, since valving of the pressure nozzle will again lead to alengthy time interval for the generation of sonic velocity which is aprerequisite of the Hartmann generator. lnterposing a variable shutterbetween the nozzle and the resonator will disrupt the shock wave frontgenerated in the cavity by the alternate filling and discharging of gasat the resonant frequency. Further, such an obstruction between thenozzle and the cup of the resonator will cause a greatly reduced outputof sound. It is proposed in the present invention to provide means formodulating sound Waves having a constant frequency, with relativelysharp break between the start and stop. It will be readily appreciatedthat a device wherein the modulation can be controlled within verynarrow limits can be extremely useful.

In order to illustrate a possible application of the present inventionthe following embodiment of the present invention is described.

The present invention is incorporated into an altitude indicating devicewherein a pulse modulation system is utilized, for control purposes, tomodulate the sonic energy transmitted by the apparatus of the presentinvention. This is achieved by the periodic filling and discharging ofthe resonator through the action of the hereinafter described cam-pistonoperation. A phase detection system is utilized, whereby phasedifference between the received signal and a reference signal determinesthe modulating frequency. In this illustration the altitude defines themodulating frequency. For example, at an altitude of 50 feet (100 feetin total travel between the transmitting device and the receivingdevice), division by the speed of sound (-1000 feet per second) providesa travel time of -0.1 second. To achieve a maximum resolution of thephase detection system, one complete cycle of the modulated sonic energyis utilized. Thus a modulating frequency of one cycle per 0.1 second orcycles per second is required at the 50 foot altitude. A modulatingfrequency higher than 10 c.p.s. would create ambiguity in the phasedetection system because more than one cycle of the modulated sonicenergy would be utilized in the phase detection sample. A frequency ofless than 10 c.p.s.

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would cause deterioration of the resolution of the phase detectionbecause less than one cycle would be utilized. These conditionsestablish the basic principle of measurement.

Thus it can be seen that a variable frequency pulse modulation techniqueis utilized, in which the modulating frequency is inversely proportionalto the altitude. The modulating frequency is established, at aparticular altitude, by comparing the phase between one complete cycleof received sonic energy and an equivalent complete cycle of a referencesignal.

ince the modulating frequency varies inversely with the altitude, theminimum measurable altitude is restricted only by the upper limit offrequency modulation. The upper limit on modulating frequency isrestricted primarily by mechanical modulator design consideration. Theseconsiderations present no problem with regard to the application as analtitude measuring device.

It is therefore a primary object of the present invention to provide animproved whistle type sonic signaling device adapted to generate timedpulses of sonic wave energy.

A further object of the present invention is to provide a whistle typesonic signaling device having a high power output, whereby a relativelyhigh percentage of unidirectional jet stream energy is converted tosonic wave pulses.

Yet a further object of the present invention is to provide simple,highly reliable pulse forming means for a whistle type sonic signalingdevice.

These and other objects and advantages of the present invention will, inpart, be pointed out with further particularity, or will, in part, beapparent from the following description and the drawing appended heretowherein:

FIG. 1 is an elevational view, partly broken away to expose the internalsupporting spider, shaft, nozzle resonator cup, of a sonic signalingdevice in the open position, or non-pulse generating condition.

FIG. 2 is an elevational view of the device of FIG. 1 in the closed orgenerating position. The figure is par tially broken away to expose thenozzle and resonator cup.

FIG. 3 is an elevational view of an alternate embodiment of the deviceshown in the non-pulse generating condition. The figure is partiallybroken away to expose the internal supporting spider, shaft, nozzleresonator cup. An electrical actuating circuit is shown schematically.

FIG. 4 shows the device of FIG. 3 with the bottom portion broken away toshow the nozzle and resonator cup in a closed condition.

Referring more particularly to the drawing, the device of the presentinvention, characterized generally by the numeral 10, comprises aconduit 12 communicating with pressurized gas inlet 14. concentricallymounted within the longitudinal bore 16 of conduit 12 is a spider 18slidably supporting a piston 20*, the functioning of which willhereinafter be described. At its lower end, conduit 12 terminates in achoked nozzle 22 having threadably secured thereto a reflector 24 whichmay, as in the illustrated embodiment, have a substantially parabolicshape. Webs 26, projecting radially inward at the open end 28 ofreflector 24 support a centrally located cylindrical hub 29 having abore 30 and a beveled seat 31.

Piston 2t is provided at its enlarged upper end 32 with biasing meanssuch as compression spring 34. Spring 34 operates between piston end 32and top surface 36 of conduit 12. Mechanically equivalent springlessconfigurations may be employed. Piston 2.0 may be actuated mechanicallyby means such as cam 38, or by conventional intermittent motion linkageswell known in the art. Alternatively, electrically energized solenoids,valves, hydraulic cylinders, or other means adapted to intermittent,repetitive motion, may be employed to displace piston 20 to the twopositions shown in the drawings.

If a gaseous fluid is made to flow out of nozzle 22,

then as a result of the Bernoulli ellect, the flow velocity will becomeequal to and greater than that of sound. As the jet stream leaves thenozzle, a characteristic pressure distribution develops. Thisdistribution is periodic in nature, and due to rapid variations in jetstream pressure and velocity, gas pile-ups and shock fronts are created.A properly positioned resonant cavity alternately becomes charged to thecorresponding jet stream pressure until a condition of unstableequilibrium is reached and then discharges backwardly into the jetstream. As a result, high intensity sonic oscillations are producedwhich are focused by reflector 24 in a desired direction. The apparatusincludes a resonant chamber 44 which is defined by bore 3i) and the topsurface 46 of plug 40. Plug 40 is provided with a beveled outer surface42 adapted to mate with beveled seat 31 in the closed condition, asshown in FIG. 2.

In the position shown in FIG. 1, with the resonator plug 40 axiallydisplaced from seat 31 by piston the sonic waves are instantaneouslydisrupted and the gas vented downwardly through central bore of sleeve29 and past the conical outside surface 42 of resonator plug 40.

It will readily be seen that displacing the resonator plug by any of thepreviously disclosed means creates time pulses which may be controlledwithin very close limits. Hence a square wave form may be readilygenerated. Due to the lengthy regenerating period associated with priorart sonic generators, this efiect was heretofore not readily achieved.

In FIGS. 3' and 4, an alternative embodiment is shown wherein theresonant chamber is opened by moving sleeve 50 away from bottom plug 52permitting gas from nozzle 22 to escape in the space there bet-ween. Inthis embodiment, bottom plug 52 is maintained in a fixed position, beingintegrally secured to spider 18 by means of tube 51. Rod 54 extendscoaxially through central bore in both tube 51 and plug 52. The upperend of rod 54 terminates at piston 2-1 and the bottom end of rod 54mounts a spider 56, the free ends of which support axially movablesleeve member 50. In FIG. 3, the apparatus is shown in thenon-resonating condition, and in FIG. 4 the sleeve member is shown inthe pulse or resonating condition.

In this embodiment, cylinder 21 is shown stroked by solenoid coil 58energized by source 60 under the control of switch 62. It will beunderstood that the mechanical stroking systems described earlier maylikewise be employed.

There has been disclosed heretofore the best embodi-.

gas can be continuously discharged into said cylinder by said nozzle;

(0) a closure member disposed transversely to said cylinder andproximate thereto at a point remote from said nozzle; and

(d) actuating means to selectively displace said closure member and saidcylinder relative to each other whereby said closure member in a firstposition is in a gas-tight, abutting relation to said cylinder to definean acoustically tuned cavity, said closure member in a second positionbeing axially displaced from said cylinder, whereby in said firstposition a sonic wave is generated by said device.

2. The device of claim 1 wherein said cylindrical hollow member ismaintained in a fixed position and said closure member is displaced.

3. The device of claim 1 wherein said cylindrical hollow member isdisplaced and said closure member is maintained in a fixed position.

4. The device of claim 1 wherein said actuating means is mechanicallystroked.

5. The device of claim 1 wherein said actuating means is electricallystroked.

6. A sonic signaling device comprising:

(a) a conduit adapted to carry gas under pressure, said conduitterminating in a convergent-divergent nozzle;

(1)) a cylindrical hollow member disposed coaxially in spacedrelationship to said nozzle, whereby said gas can be continuouslydischarged into said cylinder by said nozzle in the operationalcondition; I

(c) a closure member disposed transversely to said cylinderand'proximate thereto at. a point remote from said nozzle; and

(d) actuating means to selectively displace said closure member and.said cylinder relative to each other whereby said closure member in aifirst position is in a gas-tight, abutting relation to said cylinder todefine an acoustically tuned cavity, said closure member in a secondposition being axially displaced from said cylinder, whereby in saidfirst position a sonic wave is generated by said device and in saidsecond position said device is non-generating.

7. A sonic signaling device comprising:

(a) a conduit adapted to carry gas under pressure,

said conduit terminating in a nozzle;

(b) a cylindrical hollow member disposed coaxially in spacedrelationship to said nozzle, whereby said gas can be continuouslydischarged into said cylinder by said nozzle in the operationalcondition;

(0) a closure member disposed transversely to said cylinder andproximate thereto at a point remote from said nozzle; and

(d) actuating means to alternately displace said closure member and saidcylinder relative to each other whereby said closure member in a firstposition is in a gas-tight, abutting relation to said cylinder to definean acoustically tuned cavity, said closure member in a second positionbeing axially displaced from said cylinder, whereby in said firstposition a sonic wave is generated by said device and in said secondposition said device is non-generating.

8. The device of claim 6 wherein said'actuating means controls therelative first and second position time;

9. The device of claim 7 wherein said cylindrical hollow member ismaintained in a fixed position and said closure member is displaced.

10. The device of claim 7 wherein said cylindrical hollow member isdisplaced and said closure member is maintained in a fixed position.

11. The device of claim 7 wherein said actuating means is mechanicallystroked.

. 12. The device of claim 7 wherein said actuating means is electricallystroked.

' 13. The device of claim 7 including sonic energy focusing means inoperative relationship with said tuned cavity.

7 References Cited in the file of this patent UNITED STATES PATENTS556,291 Turner Mar. 10, 1896 1,018,310 Frey Feb. 20, 1912 1,800,512Daggett Apr. 14, 1931 2,238,668 Wellenstein Apr. 15, 1941 2,641,438Arnold June 9, 1953 2,834,570 Harrison May 13, 1958 3,064,619 FortmanNov. 20, 1962 3,070,313 Fortman Dec. 25, 1962

1. A SONIC SIGNALING DEVICE COMPRISING: (A) A CONDUIT ADAPTED TO CARRYGAS UNDER PRESSURE, SAID CONDUIT TERMINATING IN A NOZZLE; (B) ACYLINDRICAL HOLLOW MEMBER DISPOSED COAXIALLY IN SPACED RELATIONSHIP TOSAID NOZZLE, WHEREBY SAID GAS CAN BE CONTINUOUSLY DISCHARGED INTO SAIDCYLINDER BY SAID NOZZLE; (C) A CLOSURE MEMBER DISPOSED TRANSVERSELY TOSAID CYLINDER AND PROXIMATE THERETO AT A POINT REMOTE FROM SAID NOZZLE;AND (D) ACTUATING MEANS TO SELECTIVELY DISPLACE SAID CLOSURE MEMBER ANDSAID CYLINDER RELATIVE TO EACH OTHER WHEREBY SAID CLOSURE MEMBER IN AFIRST POSITION IS IN A GAS-TIGHT, ABUTTING RELATION TO SAID CYLINDER TODEFINE AN ACOUSTICALLY TUNED CAVITY, SAID CLOSURE MEMBER IN A SECONDPOSITION BEING AXIALLY DISPLACED FROM SAID CYLINDER, WHEREBY IN SAIDFIRST POSITION A SONIC WAVE IS GENERATED BY SAID DEVICE.